Problem: Christopher starts counting at 40, and he counts by threes. If 40 is the 1st number that Christopher counts. what is the 14th number that he counts?
What is the first number that he counts? $40$ What is the second number that he counts? $\begin{align*}&40 + 3 \\ &= 43\end{align*}$ What is the third number that he counts? $\begin{align*}&40 + 3 + 3 \\ &= 40 + (2 \times 3) \\ &= 46\end{align*}$ What is the 14th number that he counts? $\begin{align*}&40 + (13\times3) \\ &= 40 + 39 \\ &= 79\end{align*}$